The present invention relates to a portable domestic electric oven which utilizes rapidly recirculating heated air for cooking.
Ovens for domestic use are available on the market using a wide variety of cooking principles. The conventional electric and gas ovens which bake and broil by heating the food containing enclosure or radiating heat directly to the food are by far the most commonly used type of domestic oven. Increasing in popularity is the microwave oven which is considerably faster than the conventional ovens in cooking many types of foods. Because of the advantages associated with quick and easy cooking in a microwave oven, it is becoming increasingly common for kitchens to be equipped with the above described conventional gas or electric ovens and with microwave ovens.
In recent years the versatility of the microwave oven has been increased by adding conventional radiant elements to the microwave oven so that foods may be browned in addition to being cooked with microwaves in such combination ovens.
There are also available so-called convection ovens which resemble conventional electric ovens having radiant elements but also include fan means for circulating air within the oven to improve the heat transfer to the food being cooked and thereby speed up the cooking process. This type of air circulation, however, has not had a substantial effect on the cooking times and, therefore, the convection ovens have not been successful in the marketplace.
In order for circulating air to have a substantial effect on cooking times, it is necessary that it be heated to a sufficiently high temperature and circulated at fairly substantial velocities against the food to be cooked. There have been many commercial applications of the principles of cooking utilizing rapidly circulating heated air. Many commercial machines have been sold to restaurant chains and to commercial bakeries utilizing these principles. The patents to Smith U.S. Pat. Nos. 3,884,213; 4,154,861; 4,338,911; Henke, et al. U.S. Pat. No. 4,462,383; Burtes U.S. Pat. No. 4,576,090 and Henke U.S. Pat. No. 4,626,661 are all examples of prior art patents directed to commercial cooking apparatus utilizing high speed recirculated heated air to cook food. The patents teach the concept of directing jets of high speed heated air against the food to be cooked to improve and increase the heat transfer. In many cooking situations, there is a barrier layer of air adjacent the surface of the food which is substantially cooler than the rest of the air in the oven and provides in effect a layer of insulation which slows down or retards the cooking process. The high speed jets of heated air tend to eliminate this barrier and transfer the heat to the food more rapidly, resulting in much faster cooking.
Other examples of forced hot air baking ovens are found in the patents to Beasley, et al. U.S. Pat. No. 3,221,729; Tamada et al. U.S. Pat. No. 3,710,775; Guibert U.S. Pat. No. 4,455,478; and published under the Patent Cooperation Treaty June 15, 1987 under No. WO 87/00261 discloses a domestic electric oven which cooks by the use of recirculated heated air. The patent to Guibert U.S. Pat. No. Re. 31,756 relates to a domestic oven utilizing high velocity heated air flow but pulses the air flow intermittently to accomplish a low temperature cooking of the food. This approach seems to be in distinct contrast to the commercial type cooking apparatus which uses high temperature air and tends to cook the food at the temperature of the recirculated air.
In domestic cooking equipment, it is important that adequate provision and consideration be given the problems of cleaning and the possible problems from smoke generation. In most commercial installations, grease which might be entrained with the air circulating past the food can be trapped in filters or vented through elaborate exhaust systems. However, in the home environment any cooking appliance must be made so that it may be easily cleaned and maintained by the unskilled user of the appliance. In addition, most kitchens have inadequate exhaust systems, so it is necessary that the smoke generated be maintained at a minimum.